Method for producing fuel carburetion



Oct 30 1945- H. w. s'Ml'rH ErAL 2,387,862

METHOD FOR PRODUCING FUEL CARBURETION Filed June 16, 1944 2 Sheets-Sheetl Oct. 30, 1945. H. w. sMrrH ErAL METHOD FOR PRODUCING FUEL CARBURETIONFiled June 16, 1944 ill' E Emhr HIL 4 MTW Illustr...

Patented Oct. 30, 1945 Mn'rnon Foa Pnonncnw FUEL cAmsUna'rIoN nai-01a w.smith and nomia n. Paxton, Los Angeles, Calif.

Application June 18, 1944, Serial No. 540,614 4 Claims. (Cl. 1783-119)This invention relates to a method for producing fuel carburetion, andis a division of our co-pending application Serial No. 499,680, filedAugust 23, 1943.

In the operation of internal combustion engines, and particularlyairplane engines for military purposes, it has been found that theconsumption of liquid fuel during the period of starting an engine isexcessively high, and that it causes an engine to operate ineillciently.'I'his is particularly true when the engines are operated under lowtemperature climatic conditions, for in such cases there is diillcultyin starting the engine and properly warming it up for combat flight. Infact, it is often necessary to supply 'auxiliary heaters to heat theengine and its associated parts for one or two hours before attemptingto start the engine under its own power. In connection with theseoperations it has been found desirable to supplement or substitute theusual liquid fuel supply with fuel having the characteristics of propaneand butane, which are gaseous at normal temperature, since this type offuel will operate rapidly and efllciently in starting an engine andgetting it under conditions of flight. However, it has been found thatwhen fuels of this type are used their physical state is not constant,for under some circumstances the fuel will be in its liquid state andunder other circumstances in its vapor state. It is therefore desirableto maintain the fuel in a constant state for carburetion and to insurethat the fuel volume increases in a substantially direct ratio to theincrease in airflow into the engine as induced by engine suction. It isthe principal object of the present invention, therefore, to provide amethod of carburetion especially adapted for supplying auxiliarycarburetion to engines operating at idling speeds, and which method ischaracterized by automatically regulating the inflow of fuel to the fuelsuction line of the engine in a manner to insure that upon initialoperation of the engine adequate fuel supply will be,provided forstarting purposes, regardless of whether or not the fuel is in acomplete gaseous state, is partly gasied, or delivered to the carburetorin a liquid state, and that as the idling speed accelerates the volumeof fuel flowing to the engine intake line will increase in directproportion to the suction.

The present invention contemplates the carburetion of fuel for aninternal combustion engine. which method involves the step of auto-lmatically priming the engine with rich fuel at initial low engine speedsand thereafter interrupting the priming action and introducing a normalflow of fuel to the engine when the engine has attained a normaloperating speed.

The invention is illustrated by way of example in the accompanyingdrawings in which:

Figure l is a view indicating a schematic arrangement ot the auxiliarycarburetor with relation to an airplane engine of the radial type, andby which apparatus the present method may be practised.

Fig. 2 is a view showing a plotted graph to indicate the increase in airand fuel flow with relation to the increase in engine suction asattained by the present method.

Fig. 3 is a view in central vertical section through the auxiliarycarburetor with which the present method is practised.

Referring more particularly to the drawings,

' l0 indicates an engine fitted with a supercharger ii. The superchargerIl is formed with a suitable connection |2 leading to the usual airinlet I3. Connected to the member i2 at a point between the air inlet Iland the supercharger Il is a fuel supply pipe il. This is attached tothe carburetor unit i5 with which the present invention is concerned.The carburetor unit has a bowl I6 formed with a radial opening Il in itsside to receive the fueLsupply pipe I4. At the center of the bowl I6 isa valve chamber il.

The valve chamber is at right angles to the radial opening I1 and isformed with threaded openings Is and 20 atpits opposite ends. Theseopenings are vertically aligned. The upper opening receives a threadedvalve seat structure 2|, and the lower opening receives a threaded valveseat structure 22. A valve element 23 is disposed within the chamber Iland moves upwardly against the valve seat 2|. As will be hereinafterexplained it is normally in its closed position. A valve element 24 isdisposed within the chamber Il and moves downwardly onto the valve seat22. 'I'his valve is normally disposed in its opened position. It will beseen that chamber I8 communicates with the passageway il, and thatoutflow of fluid may pass through either of the valve seats 2i or 22when their valves are opened. The passageway through valve seat 2icommunicates with a diaphragm chamber 25 which is closed by a diaphragm26. The diaphragm 26 is xed to the stem 21 of the valve 23 at its centerand is secured over the upper end of the bowl i6 by a ring 28. The ring28 is formed with a central passageway of two different diameters, thesmaller diameter agreeing with the diameter of the diaphragm chamber25and the larger diameter agreeing with that of a pressure space 23,which isformed by a cover plate 33. The plate 33 engages the marginaledge of an upper diaphragm 3|. fine an intermediate pressure space 32.Attention is directed to the fact, however, that the upper diaphragm 3|is of larger area than the lower diaphragm 23, and that thus adifferential action will be obtained as hereinafter explained. A spacer33 is disposed between the center of the two diaphrag'ms and is formedwith an upwardly projecting threaded portion 34 which extends into athreaded opening in a rod 33. The upper end of the rod 33 is threaded at33 to receive a nut 31 and to hold a disc 33. Interposed between thedisc 33 and the upper face of the plate 33 is a spring 33 which tends tohold the diaphragms 23 and 3| upwardly and to hold the valve 23 on itsseat. A cylindrical housing 43 is formed integral with the plate 33 andcircumscribes the spring 33. The rod 33 when extending through the plate33 has a free fit with the walls of opening 4| so that atmospheric airpressure will act upon the upper face of the diaphragm 3|.

As here shown, the carburetor bowl |3 is` formed with a radiallydisposed outlet opening 42. This is threaded and receives the end ofpipe I4' connected with the suction side of the supercharger Il. At. theinner end of the radial passageway 42 is a duct 43 which communicateswith the space 32 between the diaphragms 23 and 3|. At the inner end ofthe passageway 42 there is also a duct 44 which communicates with thechamber 23 occurring beneath diaphragm 23.

The valve 24 is fitted with a stem 43 which extends downwardly throughthe valve seat structure 22 and is formed with a threaded portion 43receiving a nut 41. This threaded portion extends through the center ofa diaphragm 43. The margin of this diaphragm is held against the lowerface of the bowl I3 by the upper face of a housing 43. The housing 43 issubstantially cylindrical and is formed intermediate its ends with aninwardly extending annular partition ilange 33 which receives a valvecylinder 3|. The valve cylinder 3| extends downwardly below the flange33. Its lower end is closed by a cylinder head 32. The valve cylinder isformed with a partition 33 intermediate its ends. The partition has acentral opening 34 through it. The upper face of the partition wall 33surrounding the opening 34 is formed with a valve seat 33 upon which avalve 33 may rest. Disposed betweenthe valve 33 and the central rigidportion The diaphragms 23 and 3| dechange from liquid to gaseous statein varying degrees. The bellows 34 is subjected to external pressureproduced by fuel passing through ducts 33 in the side wall of thecylinder 3| and communicating with a cylindrical bore 33 of the housing43. The fuel entering the bore 33 is conducted from the induction line|4 through a duct 31 in the bowl I3 to a duct 33 in the housing 43.

The lower end of the housing 43 is formed with a nange 33 against whicha head 13 is secured by cap screws 1|. This head closes the lower end ofthe bore 33 and is formed with an upwardly projecting annular flange 12against which a valve cup 13 normally rests. The cup has a lowerdiscshaped portion 14 resting directly on the flange 12 and is formedwith a central passageway 13 and a plurality of other passageways 13which are arranged circumferentially around the central passageway andare separate therefrom. A cylindrical wall section 11 extends upwardlyfrom the disc portion 14 and provides a seat for a spring 13 which isdisposed between the cup 13 and the transverse partition wall 33 of thehousing 43. This tends to urge the cup to its lowermost position aslimited by the annular flange 12.

Formed centrally of the head 13 is a threaded bore 13 which receives avalve seat 33. This valve seat is formed with a central opening 3|through which a valve stem 32 extends. 'I'his stem carries a valve 33 atits upper end and a valve 34 at its lower end. The valves are spacedfrom each other so that when they move to their alternate positions thepassageway 3| will be closed. A disc 33 is associated with the valve 33so that when it moves upwardly to engage the portion 14 of the cup 13the upward movement of the valve structure will be limited. A rod 33extends upwardly from the disc and into a spring cup 31 carried by thecylinder head 32. A spring 33 is disposed within the cup and around therod and rests against the upper face of the portion 33 of the valve.'I'his spring tends to urge the valve 33 downwardly against the seat 33.and thus normally closes the passageway 3|. The lower end of the valvestem 32 is connected to a diaphragm 33 which is disposed between themember 13 and a cover plate 33. The cover plate 33 is formed with a port3| communicating with the atmosphere and delivering atmospheric air intospace 32 which occurs between the cover plate 33 and the diaphragm 33. Aspace 33 occurs between the diaphragm 33 and the member 13. This spacecommunicates with the suction side of the carof the diaphragm 43 is aspring 33. This tends to separate the valve and the diaphragm and tourge the diaphragm upwardlyv to a position against stop fingers 33 whileurging the valve down onto its seat. 'Ihe valve 33 is formed with a stem3| which extends downwardly through the opening 34 and terminates in anenlarged disc 32. The disc 32 has upwardly extending stop nngers 33which. limit the upward movement ofv 33 through a. duct 33.

buretor through a priming passageway 34. The suction pipe I4 alsocommunicates with a space The space 33 is defined between the diaphragm43 and the lower face 31 of the bowl |3. A relatively small duct 33establishes communication between the priming passageway 33 and a space33 which occurs between the diaphragm 43 and the partition wall 33 cfthe housing 43.

The ducts 44 and 33 are iitted at points intermediate their ends withrestricted oriilce plates |33 and |31, respectively. These, togetherwith the restricted orifice 33, tend to insure that there will not be anundesirable pressure drop when engine suction increases, and that thefuel entering the suction pipe |4' will be maintained at a constantincrease in volume with relation to the increase in engine suction.

In operation of the carburetor with which the present invention isconcerned it is to be understood that it is connected through thesuction pipe I4' to the conduit I2 leading from the member I3 to thesupercharger II. Under these circumstances the fuel delivered from asource of supply through the induction pipe I4 has a dennlte pressure.For the purposes of the present explanation it will be assumed that thefuel is propane and that the operating pressure is nfteen pounds gauge.This pressure is constantly imposed upon the various-fluid responsiveelements i of the carburetr. At this time the valve 24 is held open bythe spring 59 so that the fuel may pass downwardly through the valveseat 20 and into the chamber 96. At the same time fuel passes downwardlythrough the ducts 61 and 68 into the chamber 66 and from thence throughthe ports 66 into the valve cylinder 6I where it acts against thebellows 64. It is to be understood that when the engine is started undernormal temperatures the fuel will be in a gaseous state and will bedrawn through the carburetor in this state. lt is intended that the fuelshall be in a liquid state when the engine has reached its operatingtemperature. It will be evident that since the bellows 64 is partiallylled with propane that the pressure exerted by the fuel within thebellows will vary in direct relation to the fluid surrounding it. Thiswill be due to the change of the propane from its liquid state to agaseous state. at which time an increased volume of uid will prevailwithin the bellows 64 tending to move the valve stem 6I upwardly and tolift the valve 56 from its seat. It is to be pointed out that as soon asthe prevailing temperature drops to a point where the propane condensesthe valve 56 will close. This drop in temperature will be produced asthe engine speed accelerates and will cause the fuel passing through thecarburetor to change to liquid phase, and the fuel which is sealedwithin the bellows will also condense. This last action will of courserelieve the pressure exerted by the bellows and tending to lift thevalve 66 from its seat. This compensates for the conditions createdwithin the carburetor as produced by variation in the physical state ofthe propane fuel. It will be evident that the pressure of the gaseousfuel passing inwardly through the supply pipe I4 to the chamber I8within the bowl I6 will act against the diaphragm 48, and that pressurevof uid passing through valve port 54 will oppose the downward movementof the diaphragm 48 and will be equal to the pressure of the uid passingthrough valve 28. Since the pressures are balanced on both slde`s ofdiaphragm 48 valve 24 will be held open by spring 59, allowing gaseousfuel to flow through passageway 96 at full inlet pressure, therebycompensating for the changes in the physical state of the fuel passingthrough the carburetor.

During the initial stage of starting the engine, as previouslydiscussed, it is to be understood that atmospheric air pressure actingupon the diaphragm 89 through the duct 9| will tend to open the valve83. However, the springs 18 and 96 will act to close this valve. Assuction increases in the suction pipe I4' a negative pressure will beimposed upon the upper face of the diaphragm 89 through the duct 94, andthis will tend to lift the diaphragm 89 and to move the valve 83 fromits seat. Fuel from the intake pipe I4 will then bypass the entirecarburetor structure through ducts 61 and 68 and thence through thevalve opening 8I to the chamber 93, after which it will be drawndirectly into the suction line through the passageway 94. This willsupply an initially greater volume of fuel 4valve seat element 99 and tothe engine when starting and mightbe considered .as producing anautomatic priming action. When, however, the suction increases thediaphragm 89 will be lifted further, lifting cup 13, so that the valve84 will close against the priming action.

While the foregoing priming action is taking place it will be understoodthat fuel will be drawn directly from the induction pipe I4 to theeduction pipe I4' through the passageway Il to the chamber I8 in thebowl I6 and thence through the valve seat 29 to the space 85 above thediaphragm 48, after which it will be drawn through the duct 96 into theeduction or suction pipe I4. The restricted orifice IOI acts to meterthe fuel to maintain a substantially constant. volume. As previouslyexplained, it will be assumed that the pressure of the incoming fuel isfifteen pounds gauge. This fuel pressure will be imposed upon thediaphragm 48,`but the pressure of spring 59 is less than fifteen poundsgauge so that the pressure in chamber will be reduced to a Valuedetermined by spring 59 and the suction imposed on lower side ofdiaphragm 48 through duct 98, maintaining a relatively constant volumeof fuel flowing through orifice IUI, regardless of suction in pipe I4'.As the engine speed accelerates the suction in pipe I4' increases. Thisacts to close the valve 84 and impose a negative pressure within thespace 32 occurring between the diaphragms 26 and 3 I. These diaphragmsare maintained normally in their uppermost position by the expansion ofspring 39, since the diaphragm 3| is subjected to atmospheric pressure.When the negative pressure within the space 32 overcomes the pressure ofspring 39 the atmospheric pressure exerted upon the upper face of thediaphragm 3| will cause the diaphragms 26 and 3| to flex downwardly andwill move the valve 23 to an open position with relation to its valveseat 2 I. When the valve 23 moves to its open position fuel from theinduction pipe I4 will pass through the valve seat 2| into the space 25beneath the diaphragm 26 and will then be drawn through the restrictedorifice IIJU and the duct 44 to the suction pipe I 4'. It will beunderstood that when the valve 23 moves to its open position immediatelya portion of the fuel pressure is imposed upon the under face ofdiaphragm 26 and will tend to move the diaphragm upwardly and close thevalve 23. However, the pressure area of the upper diaphragm 3| isgreater than that of the diaphragm 26 and will oppose the closing actionof the valve, regulating the pressure in chamber 25 to a valuedetermined by the suction in space 32. 'Ihe spring 39 will act as anintermediate variable factor between the two diaphragms in addition totheir pressure area differences and will insure that a suction is builtup in the line I4'. The volume of fuel drawn to the engine through thecarburetor I5 will be increased proportionately to the increase insuction, to maintain a relatively constant ratio of the fuel to the airpassing into the engine. 'I'his action is more particularly indicated inthe graph here disclosed as Fig. 2, where it will be seen that while thesuction-airow varies somewhat from an absolute progressive ratio, andthat the suction-fuelow varies somewhat from an absolute progressiveratio that the mean factors indicated by these two curves demonstratethat in the present device the fuel quantity flow progresses insubstantially direct proportion to the airow.

It will thus be seen that the method here diswill prevent a furtherclosed provides a simple fuel control whereby a fuel, such as propane.may be delivered to carburetion apparatus for engine starting, and willproduce a preliminary priming action. while in liquid phase and willtend to be` converted to vapor phase for normal engine operations.

While we have shown the preferred method of practising our invention, itis to be understood that various changes in the steps of the operationmay be made by those skilled in the art without departing from thespirit of the invention as claimed.

Having thus described our invention. what we claim and desire to secureby letters Patent is:

1. A method of fuel control for carburetion in combination with aninternal combustion engine, which fuel is characterized as being gaseousat normal temperatures and liquid at subnormal temperatures. said methodconsisting in delivering said fuel under pressure to a control structureand withdrawing fuel therefrom under engine suction, establishing a pathof fluid flow from the induction to the eduction sides of said controlstructure, interposlng a control valve in said path of travel normallyheld open, establishing a fluid flow from the induction to the eductionsides of said control structure, interposing an entrapped quantity ofthe fluid at a point in said last named path of travel and associatingsaid quantity of entrapped fluid with said valve, whereby as thetemperature of entrapped uid is reduced by the flowing fluid the valvewill be'moved toward a closed position.

2. A method of fuel control for carburetion in combination with aninternal combustion engme. which fuel is characterized as being gaseousat normal temperatures and liquid at subnormal temperatures, said methodconsisting in delivering said fuel under pressure to a control structureand withdrawing fuel therefrom under engine suction, establishing a pathof fluid flow from the induction to the eduction sides of said controlstructure, interposlng a pressure regulating valve in said path oftravel normally held open, providing a normal feed path of travel offuel from the induction passageway to the eductlon pas' sageway,interposing an initially closed valve in arenoso said path of travel.and providing means subject to increased suction action whereby thevalve in the normal feed path o! travel will open as the engine'speedaccelerates.

3. A method of fuel control for carburetion in combination with aninternal combustion. engine, which fuel is characterised as beinggaseous at normal temperatures and liquid at subnormal temperatures.said method consisting in delivering said fuel under pressure to controlstructure and withdrawing fuel there under engine suction, establishinga path ofjuid flow from the induction to the eduction of said controlstructure along which a primihg feed of fuel takes place. interposing apressure regulating valve in said path of travel, whereby apredetermined degree of suction on the eduction side of the control unitwill tend to decrease the opening of the valve as the engine speedincreases, establishing a normal feed path of travel for fuel from theinduction to the eduction sides of the unit, interposing an initiallyclosed valve therein and providing means responsive to suction on theeduction side of the unit tending to open the valve in the normal feedpath of travel as the engine speed accelerates.

4. A method of controlling a fuel. which is characterized as beinggaseous at normal temperatures and liquid at subnormal temperatures andwhich fuel is delivered to the induction equipment of an internalcombustion engine from a source of saidfiuid under pressure and througha control device having a priming passageway fitted with a pressureregulating valve responsive to engine suction and a normal feedpassageway initially closed and responsive to engine suction, whichmethod consists in delivering fuel under pressure to said controldevice, subjecting the control device to engine suction, whereby thepriming flow valve will tend to close as engine speed accelerates, andsubjecting the feed valve to engine suction whereby the feed valve willgradually open al engine speed accelerates to increase the fuel supplyvolume to the engine in substantially direct proportion to increase inengine suction.

HAROLD W. SMITH. DONAID D. PAXTON.

